Structure and Photophysics of N-Tolanyl-phenochalcogenazines and their Radical Cations.

The study focuses on the structural and photophysical characteristics of neutral and oxidized forms of N-tolanyl-phenochalcogenazines PZX-tolan with X=O, S, Se, and Te. X-ray crystal structure analyses show a pseudo-equatorial (pe) structure of the tolan substituent in the O, S, and Se dyads, while the Te dyad possesses a pseudo-axial (pa) structure. DFT calculations suggest the pe structure for O and S, and the pa structure for Se and Te as stable forms. Steady-state and femtosecond-time resolved optical spectroscopy in toluene solution indicate that the O and S dyads emit from a CT state, whereas the Se and Te dyads emit from a tolan-localized state. The T1 state is tolan-localized in all cases, showing phosphorescence at 77 K. The heavy atom effect of chalcogens induces intersystem crossing from S1 to Tx, resulting in a decreasing S1 lifetime from 2.1 ns to 0.42 ps. The T1 states possess potential for singlet oxygen sensitization with a high quantum yield (ca. 40 %) for the O, S, and Se dyads. Radical cations exhibit spin density primarily localized at the heterocycle. EPR measurements and quasirelativistic DFT calculations reveal a very strong g-tensor anisotropy, supporting the pe structure for the S and Se derivatives.

Trapping of a Transient Base-Stabilised Alumylene and Alumylene-Type Reactivity of a Self-Stabilising Dialumene towards Organic Azides.

The reduction of a carbene-coordinated, sterically encumbered terphenyl-substituted aluminium diiodide, (LRAlI2 ), yielded a "masked" dialumene (LRAl=AlRL), self-stabilised through [2+2] cycloaddition with a peripheral aromatic group. During the course of the reaction, a carbene-stabilised arylalumylene (LRAl:) was generated in situ, which was trapped using an alkyne, generating an aluminacyclopropene or a C-H activated product thereof, depending on the steric bulk of the alkyne. The masked dialumene also underwent intramolecular cycloreversion and dissociation into alumylene fragments, which reacted with various organic azides to yield monomeric or dimeric iminoalanes depending on the sterics of the azide substituent. The thermodynamics of monomeric and dimeric iminoalane formation were probed by theoretical calculations.

Unlocking Heteroaromatic Ring Systems through Chalcogen Insertion into Boroles.

In this work, we report the reactivity of various annulated borole derivatives toward chalcogen (O, S, and Se) insertion. Among a series of 9-borafluorenes with different boron substituents (Ph, Br, or o-carboranyl) and a mixed thiophene-benzene-fused derivative, only the 9-o-carboranyl-substituted 9-borafluorene yielded the complete set of chalcogen-containing heteroarenes, including the first 1,2-selenaborinine derivative. To evaluate the aromaticity of this heterocyclic analogue of phenanthrene, nucleus-independent chemical shift (NICS) values were computed and compared to those of its lighter group 16 congeners.

Loss of Agrp1 in zebrafish: Effects on the growth and reproductive axis.

Loss of agouti related neuropeptide (AgRP) does not lead to overt phenotypes in mammals unless AgRP neurons are ablated. In contrast, in zebrafish it has been shown that Agrp1 loss of function (LOF) leads to reduced growth in Agrp1 morphant as well as Agrp1 mutant larvae. Further, it has been shown that multiple endocrine axes are dysregulated upon Agrp1 LOF in Agrp1 morphant larvae. Here we show that adult Agrp1 LOF zebrafish show normal growth and reproductive behavior in spite of a significant reduction in multiple related endocrine axes namely reduced expression in pituitary growth hormone (gh) follicle stimulating hormone (fshb) as well as luteinizing hormone (lhb). We looked for compensatory changes in candidate gene expression but found no changes in growth hormone and gonadotropin hormone receptors that would explain the lack of phenotype. We further looked at expression in the hepatic and muscular insulin-like growth factor (Igf) axis which appears to be normal. Fecundity as well as ovarian histology also appear largely normal while we do see an increase in mating efficiency specifically in fed but not fasted AgRP1 LOF animals. This data shows that zebrafish can grow and reproduce normally in spite of significant central hormone changes and suggests a peripheral compensatory mechanism additional to previously reported central compensatory mechanisms in other zebrafish neuropeptide LOF lines.

Redefining the role of surgery in early small-cell lung cancer.

PURPOSE: Resection is guideline recommended in stage I small-cell lung cancer (SCLC) but not in stage II. In this stage, patients are treated with a non-surgical approach. The aim of this meta-analysis was to assess the role of surgery in both SCLC stages. Surgically treated patients were compared to non-surgical controls. Five-year survival rates were analysed. METHODS: A systematic literature search was performed on December 01, 2021 in Medline, Embase and Cochrane Library. Studies published since 2004 on the effect of surgery in SCLC were considered and assessed using ROBINS-I. We preformed I2-tests, Q-statistics, DerSimonian-Laird tests and Egger-regression. The meta-analysis was conducted according to PRISMA. RESULTS: Out of 6826 records, we identified seven original studies with a total of 15,170 patients that met our inclusion criteria. We found heterogeneity between these studies and ruled out any publication bias. Patient characteristics did not significantly differ between the two groups (p-value > 0.05). The 5-year survival rates in stage I were 47.4 ± 11.6% for the 'surgery group' and 21.7 ± 11.3% for the 'non-surgery group' (p-value = 0.0006). Our analysis of stage II SCLC revealed a significant survival benefit after surgery (40.2 ± 21.6% versus 21.2 ± 17.3%; p-value = 0.0474). CONCLUSION: Based on our data, the role of surgery in stage I and II SCLC is robust, since it improves the long-term survival in both stages significantly. Hence, feasibility of surgery as a priority treatment should always be evaluated not only in stage I SCLC but also in stage II, for which guideline recommendations might have to be reassessed.

Stage I and II Small-Cell Lung Cancer-New Challenge for Surgery.

PURPOSE: The recommended treatment for small-cell lung cancer (SCLC) currently is surgery in stage I disease. We wondered about stage II SCLC and present a meta-analysis on mean-survival of patients that underwent surgery for stage I and II compared to controls. METHODS: A systematic literature search was performed on December 01st 2021 in Medline, Embase and Cochrane Library. We considered studies published on the effect of surgery in SCLC since 2004 and assessed them using ROBINS-I. We preformed I2-tests, Q-statistics, DerSimonian-Laird tests and Egger-regression. The meta-analysis was conducted according to PRISMA. RESULTS: Out of 6826 records, seven studies with a total of 11,241 patients ('surgery group': 3911 patients; 'non-surgery group': 7330; treatment period: 1984-2015) were included. Heterogeneity between the studies was revealed in absence of any publication bias. Patient characteristics did not differ between the groups (p-value > 0.05). The mean-survival in an analysis of patients in stage I was 36.7 ± 10.8 months for the 'surgery group' and 20.3 ± 5.7 months for the 'non-surgery group' (p-value = 0.0084). A combined analysis of patients in stage I and II revealed a mean-survival of 32.0 ± 16.7 months for the 'surgery group' and 19.1 ± 6.1 months for the 'non-surgery group' (p-value = 0.0391). In a separate analysis of stage II, we were able to demonstrate a significant survival benefit after surgery (21.4 ± 3.6 versus 16.2 ± 3.9 months; p-value = 0.0493). CONCLUSION: Our meta-analysis shows a significant survival benefit after surgery not only in the recommended stage I but also in stage II SCLC. Our data suggests that both stages should be considered for surgery of early SCLC.

Identification of targeted therapy options for gastric adenocarcinoma by comprehensive analysis of genomic data.

BACKGROUND: So far only trastuzumab, pembrolizumab and ramucirumab have been approved by the FDA for targeted therapy in gastric cancer (GC). Here we report on potential targeted therapy options for gastric adenocarcinoma based on a novel analysis of "The Cancer Genome Atlas (TCGA)" database. METHODS: One hundred two FDA-approved targeted cancer drugs were compiled and molecular targets defined. Drugs were considered as potentially effective if targeted genes showed (1) an increase in copy number, (2) gain of function with oncogene activation, (3) specific alterations responsive to approved drugs. Additionally, genetic changes that confer drug resistance and/or sensitivity were evaluated. RESULTS: Fifty percentage of patients with GC may be treatable with non-GC but FDA-approved targeted cancer therapies. The major drug identified in our in silico study for GC is copanlisib, a PI3K inhibitor. In the TCGA patient database, our genetically based drug response prediction identified more patients with alterations sensitive to copanlisib compared to the already-GC-approved drug trastuzumab (20%, 78 out of 393 patients, vs. trastuzumab: 13%, 52 of 393 patients), which is mainly due to the high incidence of PIK3CA gain of function mutations within mutation hot spots. CONCLUSION: Our results demonstrate that various currently FDA-approved drugs might be candidates for targeted therapy of GC. For clinical trials, cancer patients should be selected based on the genomic profile of their tumor.

Diborane(4) Azides: Surprisingly Stable Sources of Transient Iminoboranes.

Herein we describe the first examples of isolable electron-precise diboranes(4) that bear azide moieties: the acyclic 1,2-diazido-1,2-bis(dimethylamino)diborane(4) and the cyclic 1,4-diaryl-2,3-diazido-1,4-diaza-2,3-diborinines (aryl=mesityl, 2,6-xylyl, 4-tolyl). The reported examples are not only stable enough to be observed and isolated (putative transient diborane(4) azides previously reported by our group spontaneously decompose even below room temperature), but some of them are even robust enough to undergo controlled pyrolysis without explosive decomposition at temperatures well above 100 °C. In two cases, the controlled pyrolysis allows the isolation of complex diazaboretidines, which are the apparent dimerization products of endocyclic boryl-iminoboranes.

Leptin signaling regulates glucose homeostasis, but not adipostasis, in the zebrafish.

Leptin is the primary adipostatic factor in mammals. Produced largely by adipocytes in proportion to total adipose mass, the hormone informs the brain regarding total energy stored as triglycerides in fat cells. The hormone acts on multiple circuits in the brain to regulate food intake, autonomic outflow, and endocrine function to maintain energy balance. In addition to regulating adipose mass, mammalian leptin also plays a role in the regulation of glucose homeostasis and as a gating factor in reproductive competence. Leptin-deficient mice and people exhibit early onset profound hyperphagia and obesity, diabetes, and infertility. Although leptin and the leptin receptor are found in fish, the hormone is not expressed in adipose tissue, but is found in liver and other tissues. Here, we show that adult zebrafish lacking a functional leptin receptor do not exhibit hyperphagia or increased adiposity, and exhibit normal fertility. However, leptin receptor-deficient larvae have increased numbers of ß-cells and increased levels of insulin mRNA. Furthermore, larval zebrafish have been shown to exhibit ß-cell hyperplasia in response to high fat feeding or peripheral insulin resistance, and we show here that leptin receptor is required for this response. Adult zebrafish also have increased levels of insulin mRNA and other alterations in glucose homeostasis. Thus, a role for leptin in the regulation of ß-cell mass and glucose homeostasis appears to be conserved across vertebrates, whereas its role as an adipostatic factor is likely to be a secondary role acquired during the evolution of mammals.

Saccharomyces cerevisiae variety diastaticus friend or foe?-spoilage potential and brewing ability of different Saccharomyces cerevisiae variety diastaticus yeast isolates by genetic, phenotypic and physiological characterization.

Saccharomyces cerevisiae variety diastaticus is generally considered to be an obligatory spoilage microorganism and spoilage yeast in beer and beer-mixed beverages. Their super-attenuating ability causes increased carbon dioxide concentrations, beer gushing and potential bottle explosion along with changes in flavor, sedimentation and increased turbidity. This research shows clear differences in the super-attenuating properties of S. cerevisiae var. diastaticus yeast strains and their potential for industrial brewing applications. Nineteen unknown spoilage yeast cultures were obtained as isolates and characterized using a broad spectrum of genetic and phenotypic methods. Results indicated that all isolates represent genetically different S. cerevisiae var. diastaticus strains except for strain TUM PI BA 124. Yeast strains were screened for their super-attenuating ability and sporulation. Even if the STA1 gene responsible for super-attenuation by encoding for the enzyme glucoamylase could be verified by real-time polymerase chain reaction, no correlation to the spoilage potential could be demonstrated. Seven strains were further characterized focusing on brewing and sensory properties according to the yeast characterization platform developed by Meier-Dörnberg. Yeast strain TUM 3-H-2 cannot metabolize dextrin and soluble starch and showed no spoilage potential or super-attenuating ability even when the strain belongs to the species S. cerevisiae var. diastaticus. Overall, the beer produced with S. cerevisiae var. diastaticus has a dry and winey body with noticeable phenolic off-flavors desirable in German wheat beers.

Prognostic Impact of Extracapsular Lymph Node Invasion on Survival in Non-small-Cell Lung Cancer: A Systematic Review and Meta-analysis.

The extracapsular tumor extension (ECE) of nodal metastasis is an important prognostic factor in different types of malignancies. However, there is a lack of recent data in patients with non-small-cell lung cancer (NSCLC). In addition, the TNM staging system does not include ECE status as a prognostic factor. This systematic review and meta-analysis has been conducted to summarize and pool existing data to determine the prognostic role of ECE in patients with lymph node-positive NSCLC. Two authors performed an independent search in PubMed using a predefined keyword list, without language restrictions with publication date since 1990. Prospective or retrospective studies reporting data on prognostic parameters in subjects with NSCLC with positive ECE or with only intracapsular lymph node metastasis were retrieved. Data were summarized using risk ratios (RR) for the survival with 95% confidence intervals (CI). The data was analyzed using Mix 2 (ref: Bax L: MIX 2.0 - Professional software for meta-analysis in Excel. Version 2.015. BiostatXL, 2016. https://www.meta-analysis-made-easy.com ). There 2,105 studies were reviewed. Five studies covering a total of 828 subjects met the inclusion criteria and were included in the meta-analysis. Two hundred and ninety-eight (35.9%) patients were categorized as ECE+, of whom 54 (18.1%) survived at the end of follow-up. In the ECE-negative group, 257 patients (48.4%) survived by the end of follow-up. Thus, ECE status is associated with a significantly decreased survival rate: pooled RR 0.45 (95% CI 0.35-0.59), Q (4) = 4.06, P value = 0.39, and I 2 = 68.00% (95 CI 0.00-79.55%). In conclusion, ECE has a significant impact on survival in NSCLC patients and should be considered in diagnostic and therapeutic decisions in addition to the current TNM staging. Postoperative radiotherapy may be an option in ECE-positive pN1 NSCLC patients.

Screening for new brewing yeasts in the non-Saccharomyces sector with Torulaspora delbrueckii as model.

This study describes a screening system for future brewing yeasts focusing on non-Saccharomyces yeasts. The aim was to find new yeast strains that can ferment beer wort into a respectable beer. Ten Torulaspora delbrueckii strains were put through the screening system, which included sugar utilization tests, hop resistance tests, ethanol resistance tests, polymerase chain reaction fingerprinting, propagation tests, amino acid catabolism and anabolism, phenolic off-flavour tests and trial fermentations. Trial fermentations were analysed for extract reduction, pH drop, yeast concentration in bulk fluid and fermentation by-products. All investigated strains were able to partly ferment wort sugars and showed high tolerance to hop compounds and ethanol. One of the investigated yeast strains fermented all the wort sugars and produced a respectable fruity flavour and a beer of average ethanol content with a high volatile flavour compound concentration. Two other strains could possibly be used for pre-fermentation as a bio-flavouring agent for beers that have been post-fermented by Saccharomyces strains as a consequence of their low sugar utilization but good flavour-forming properties.

Protein phosphatase-dependent circadian regulation of intermediate-term associative memory.

The endogenous circadian clock is a principal factor modulating memory across species. Determining the processes through which the circadian clock modulates memory formation is a key issue in understanding and identifying mechanisms to improve memory. We used the marine mollusk Aplysia californica to investigate circadian modulation of intermediate-term memory (ITM) and the mechanisms through which the circadian clock phase specifically suppresses memory using the operant learning paradigm, learning that food is inedible. We found that ITM, a temporally and mechanistically distinct form of memory, is rhythmically expressed under light-dark and constant conditions when induced by either massed or spaced training. Strong circadian regulation of ITM occurs with memory exhibited only by animals trained during the early subjective day; no apparent memory is expressed when training occurs during the late subjective day or night. Given the necessity of multiple persistent kinase cascades for ITM, we investigated whether protein phosphatase activity affected circadian modulation. Inhibition of protein phosphatases 1 and 2A blocked ITM when animals were trained during the early (subjective) day while resulting in phase-specific memory rescue when animals were trained late in the subjective day and early night. In contrast, inhibition of calcineurin did not block ITM when animals were trained during the early day and permitted ITM when animals were trained during the late subjective day, early evening, and throughout the night. These results demonstrate that levels of protein phosphatase activity are critical regulators of ITM and one mechanism through which the circadian clock regulates memory formation.

Postoperative Tobacco Cessation Improves Quality of Life, Lung Function and Long-Term Survival in Non-Small-Cell Lung Cancer Patients.

OBJECTIVES: About 90% of all non-small cell lung cancer (NSCLC) cases are associated with inhalative tabacco smoking. Half of patients continue smoking during lung cancer therapy. We examined the effects of postoperative smoking cessation on lung function, quality of life (QOL) and long-term survival. MATERIALS AND METHODS: In total, 641 patients, who underwent lobectomy between 2012 and 2019, were identified from our single institutional data base. Postoperatively, patients that actively smoked at the time of operation were offered a structured 'smoking cessation' program. For this retrospective analysis, two patient groups (total n = 90) were selected by pair matching. Group A (n = 60) had no postoperative tobacco smoking. Group B (n = 30) involved postoperative continued smoking. Lung function (FEV1, DLCO) and QOL ('SF-36' questionnaire) were measured 12 months postoperatively. We compared long-term outcomes using Kaplan-Meier curves. RESULTS: The mean age in group A was 62.6 ± 12.5 years and that in group B was 64.3 ± 9.7 years (p = 0.82); 64% and 62%, respectively, were male (p = 0.46). Preoperative smoking habits were similar ('pack years': group A, 47 ± 31; group B, 49 ± 27; p = 0.87). All relevant baseline characteristics we collected were similar (p > 0.05). One year after lobectomy, FEV1 was reduced by 15% in both groups (p = 0.98). Smoking cessation was significantly associated with improved DLCO (group A: 11 ± 16%; group B: -5 ± 14%; p <0.001) and QOL (vitality (VT): +10 vs. -10, p = 0.017; physical role function (RP): +8 vs. -17, p = 0.012; general health perceptions (GH): +12 vs. -5, p = 0.024). Patients who stopped smoking postoperatively had a significantly superior overall survival (median survival: 89.8 ± 6.8 [95% CI: 76.6-103.1] months vs. 73.9 ± 3.6 [95% CI: 66.9-80.9] months, p = 0.034; 3-year OS rate: 96.2% vs. 81.0%, p = 0.02; 5-year OS rate: 80.0% vs. 64.0%, p = 0.016). The hazard ratio (HR) was 2.31 [95% CI: 1.04-5.13] for postoperative smoking versus tobacco cessation. CONCLUSION: Postoperative smoking cessation is associated with improved quality of life and lung function testing. Notably, a significant increase in long-term survival rates among non-smoking NSCLC patients was observed. These findings could serve as motivation for patients to successfully complete a non-smoking program.

Closing the RCT Gap-A Large Meta-Analysis on the Role of Surgery in Stage I-III Small Cell Lung Cancer Patients.

INTRODUCTION: Despite clear guideline recommendations, surgery is not consistently carried out as part of multimodal therapy in stage I small cell lung cancer (SCLC) patients. The role of surgery in stages II and III is even more controversial. In the absence of current randomized control trials (RCT), we performed a meta-analysis comparing surgery versus non-surgical treatment in stage I to III SCLC patients. METHODS: A systematic review of the literature was conducted on 1 July 2023, focusing on studies pertaining to the impact of surgery on small cell lung cancer (SCLC). These studies were evaluated using the ROBINS-I tool. Statistical analyses, including I² tests, Q-statistics, DerSimonian-Laird tests, and Egger regression, were performed to assess the data. In addition, 5-year survival rates were analyzed. The meta-analysis was conducted according to PRISMA standards. RESULTS: Among the 6826 records identified, 10 original studies encompassing a collective cohort of 95,323 patients were incorporated into this meta-analysis. Heterogeneity was observed across the included studies, with no discernible indication of publication bias. Analysis of patient characteristics revealed no significant differences between the two groups (p-value > 0.05). The 5-year survival rates in a combined analysis of patients in stages I-III were 39.6 ± 15.3% for the 'surgery group' and 16.7 ± 12.7% for the 'non-surgery group' (p-value < 0.0001). SCLC patients in stages II and III treated outside the guideline with surgery had a significantly better 5-year survival compared to non-surgery controls (36.3 ± 20.2% vs. 20.2 ± 17.0%; p-value = 0.043). CONCLUSIONS: In the absence of current RCTs, this meta-analysis provides robust suggestions that surgery might significantly improve survival in all SCLC stages. Non-surgical therapy could lead to a shortening of life. The feasibility of surgery in non-metastatic SCLC should always be evaluated as part of a multimodal treatment.

Transition-metal-like coordination chemistry of dicoordinate borylenes with organic azides.

The photolytic or oxidative liberation of a cyclic (amino)(alkyl)carbene (CAAC)-stabilized arylborylene in the presence of organoazides yielded borylene-organoazide complexes (4a,b) has been achieved in a manner akin to the first step of the Staudinger reaction. Similarly, a CAAC-stabilized aminoborylene also afforded borylene-organoazide complexes (6a-c), which further undergo rearrangement to produce aminoborane triazene species (7a,b).

Massed training-induced intermediate-term operant memory in aplysia requires protein synthesis and multiple persistent kinase cascades.

The Aplysia feeding system with its high degree of plasticity and well characterized neuronal circuitry is well suited for investigations of memory formation. We used an operant paradigm, learning that food is inedible (LFI), to investigate the signaling pathways underlying intermediate-term memory (ITM) in Aplysia. During a single massed training session, the animal associates a specific seaweed with the failure to swallow, generating short-term (30 min) and long-term (24 h) memory. We investigated whether the same training protocol induced the formation of ITM. We found that massed LFI training resulted in temporally distinct protein synthesis-dependent memory evident 4-6 h after training. Through in vivo experiments, we determined that the formation of ITM required protein kinase A, protein kinase C, and MAPK. Moreover, the maintenance of ITM required PKA, PKM Apl III, and MAPK because inhibition of any of these kinases after training or before testing blocked the expression of memory. In contrast, additional experiments determined that the maintenance of long-term memory appeared independent of PKM Apl III. Using Western blotting, we found that sustained MAPK phosphorylation was dependent upon protein synthesis, but not PKA or PKC activity. Thus, massed training-induced intermediate-term operant memory requires protein synthesis as well as persistent or sustained kinase signaling for PKA, PKC, and MAPK. While short-, intermediate-, and long-term memory are induced by the same training protocol, considerable differences exist in both the combination and timing of signaling cascades that induce the formation and maintenance of these temporally distinct memories.

Cyclic alkyl(amino)iminates (CAAIs) as strong 2σ,4π-electron donor ligands for the stabilisation of boranes and diboranes(4): a synthetic and computational study.

Singly and doubly cyclic alkyl(amino)iminate (CAAI)-substituted boranes and diboranes(4) were synthesised by halosilane elimination between a silylimine and halo(di)borane precursors. 11B NMR-spectroscopic studies show that the CAAI ligand is a much stronger electron donor than amino ligands. X-ray crystallographic analyses reveal that the degree of B-NCAAI double bonding increases with the electron-withdrawing capacity of the other substituents at boron. The C-N-B bond angle displays a great flexibility, ranging from 131° to near-linear 176°, the narrowest angles being observed for NMe2-substituted derivatives and the widest angles for highly sterically demanding substituents. Density functional theory (DFT) calculations on the electronic structures of the anionic CAAI ligand compared to unsaturated and saturated N-heterocyclic iminate (NHI) ligands show that the former is the best σ donor of the three but less π-donating than the unsaturated NHI. Nevertheless, the linear (CAAI)BH2 complex displays somewhat stronger C-N and N-B π bonding than the corresponding ((S)NHI)BH2 complexes.

PKA and PKC are required for long-term but not short-term in vivo operant memory in Aplysia.

We investigated the involvement of PKA and PKC signaling in a negatively reinforced operant learning paradigm in Aplysia, learning that food is inedible (LFI). In vivo injection of PKA or PKC inhibitors blocked long-term LFI memory formation. Moreover, a persistent phase of PKA activity, although not PKC activity, was necessary for long-term memory. Surprisingly, neither PKA nor PKC activity was required for associative short-term LFI memory. Additionally, PKA and PKC were not required for the retrieval of short- or long-term memory (STM and LTM, respectively). These studies have identified key differences between the mechanisms underlying nonassociative sensitization, operant reward learning, and LFI memory in Aplysia.

PKG-mediated MAPK signaling is necessary for long-term operant memory in Aplysia.

Signaling pathways necessary for memory formation, such as the mitogen-activated protein kinase (MAPK) pathway, appear highly conserved across species and paradigms. Learning that food is inedible (LFI) represents a robust form of associative, operant learning that induces short- (STM) and long-term memory (LTM) in Aplysia. We investigated the role of MAPK signaling in LFI memory in vivo. Inhibition of MAPK activation in animals prior to training blocked STM and LTM. Discontinuing MAPK signaling immediately after training inhibited LTM with no impact on STM. Therefore, MAPK signaling appears necessary early in memory formation for STM and LTM, with prolonged MAPK activity required for LTM. We found that LFI training significantly increased phospho-MAPK levels in the buccal ganglia. Increased MAPK activation was apparent immediately after training with greater than basal levels persisting for 2 h. We examined the mechanisms underlying training-induced MAPK activation and found that PKG activity was necessary for the prolonged phase of MAPK activation, but not for the early MAPK phase required for STM. Furthermore, we found that neither the immediate nor the prolonged phase of MAPK activation was dependent upon nitric oxide (NO) signaling, although expression of memory was dependent on NO as previously reported. These studies emphasize the role of MAPK and PKG in negatively reinforced operant memory and demonstrate a role for PKG-dependent MAPK signaling in invertebrate associative memory.